U.S. patent application number 12/532792 was filed with the patent office on 2010-04-01 for apparatus for processing utility waste with bioderadable organic material content.
This patent application is currently assigned to Veolia Bioenergy Europe Kft. Invention is credited to Gyozo Barabas, Istvan Hajd, Erno Pall, Mihaly Szilagyi, Ferenc Torocsik.
Application Number | 20100078512 12/532792 |
Document ID | / |
Family ID | 38336868 |
Filed Date | 2010-04-01 |
United States Patent
Application |
20100078512 |
Kind Code |
A1 |
Pall; Erno ; et al. |
April 1, 2010 |
APPARATUS FOR PROCESSING UTILITY WASTE WITH BIODERADABLE ORGANIC
MATERIAL CONTENT
Abstract
An apparatus containing crushing screws (11) of the same pitch
direction and without central shaft, provided with short drive
shafts (112) on their driven end, wherein the rotational axis of
the discharging screw (151) and the plane determined by the
rotational axes of the two crushing screws (11) define an acute
angle.
Inventors: |
Pall; Erno; (Budapest,
HU) ; Torocsik; Ferenc; (Szolnok, HU) ;
Barabas; Gyozo; (Erd, HU) ; Szilagyi; Mihaly;
(Budapest, HU) ; Hajd ; Istvan; (Besenyszog,
HU) |
Correspondence
Address: |
HAHN & VOIGHT PLLC
1012 14TH STREET, NW, SUITE 620
WASHINGTON
DC
20005
US
|
Assignee: |
Veolia Bioenergy Europe Kft
Budapest
HU
|
Family ID: |
38336868 |
Appl. No.: |
12/532792 |
Filed: |
March 27, 2008 |
PCT Filed: |
March 27, 2008 |
PCT NO: |
PCT/HU08/00030 |
371 Date: |
November 5, 2009 |
Current U.S.
Class: |
241/260.1 ;
241/261; 241/82.1 |
Current CPC
Class: |
Y02W 30/40 20150501;
C12M 33/16 20130101; Y02E 50/343 20130101; C12M 27/02 20130101;
Y02W 30/47 20150501; C12M 45/02 20130101; Y02W 30/43 20150501; Y02E
50/30 20130101; C02F 3/286 20130101; C12M 21/04 20130101; C02F
11/04 20130101 |
Class at
Publication: |
241/260.1 ;
241/261; 241/82.1 |
International
Class: |
B02C 19/22 20060101
B02C019/22 |
Foreign Application Data
Date |
Code |
Application Number |
Mar 28, 2007 |
HU |
P0700246 |
Claims
1-7. (canceled)
8. A crushing and sorting apparatus preferably for processing
wastes and sewage sludge with biodegradable organic material
content, comprising receiving tray, crushing screws and driving
units, wherein the bottom plate (102) of the receiving tray (10) is
perforated and formed as a screw house with an open upper part for
receiving a twin screw, two crushing screws (11) are arranged in
said screw house; a chamber (103) is formed under the bottom plate
(102) in order to accommodate one or more stirring screws; and a
discharging assembly (15) having a discharging screw (151) is
arranged at the end of the receiving tray (10) opposite to the
crushing screw driving unit, in such a way that the free end of the
discharging screw (151) opposite to the discharging screw driving
unit intrudes into the operational space of the receiving tray
(10), characterized by that the crushing screws (11) are screws of
the same pitch direction and without central shaft, provided with
short drive shafts (112) on their driven end, wherein the
rotational axis of the discharging screw (151) and the plane
determined by the rotational axes of the two crushing screws (11)
define an acute angle.
9. The crushing and sorting apparatus of claim 8, characterized by
that a plurality of briar teeth (106) are arranged on the end plate
(105) of the receiving tray (10) and a plurality of bits (111) are
arranged on the end of the crushing screw (11).
10. The crushing and sorting apparatus of claim 9, characterized by
that the pitches of crushing screws (11) are identical with each
other.
11. The crushing and sorting apparatus of claim 8, characterized by
that the crushing screws (11) are made of multilayer metal
sheets.
12. The crushing and sorting apparatus of claim 8, characterized by
that the non-driven end of the crushing screws (11) is arranged
close to the end wall.
13. The crushing and sorting apparatus of claim 8, characterized by
that the crushing screws (11) are adapted to rotate independently
of each other and their rotational speed is adjustable.
14. The crushing and sorting apparatus of claim 8, characterized by
that the discharging screw (151) is adapted for turning
back-and-forth.
15. The crushing and sorting apparatus of claim 8, characterized by
that there are one or more separate discharge hoppers (153, 154) on
the discharging assembly (15).
16-19. (canceled)
Description
[0001] The invention relates to a method of processing utility
waste of the type of biomass, in particular sewage sludge, wastes
of animal protein processing, wastes of dairy industry, kitchen
wastes, greasy sewage, etc. having organic material content.
[0002] The invention also relates to the arrangement of crushing
and sorting unit and the heat treatment/mixing unit of the system
for implementing the method according to the invention.
[0003] Due to the increasingly stricter regulations of environment
protection, the problem of treating and degrading/eliminating
wastes containing organic materials becomes more and more
severe.
[0004] As a result of the sewage purification technologies, an
extremely high amount of sewage sludge containing organic materials
is produced in the sewage purification plants of the
settlements.
[0005] The problem of treatment of sewage sludge can be regarded as
solved. In the most common solution, the properly concentrated
sewage sludge is fed into a mezophilic and/or thermophilic
fermentation tank, in which, after an anaerobic treatment, biogas
releases from the organic material component. This biogas is
typically used for in-situ production of electricity.
[0006] For utilizing wastes containing organic materials, there
have been various methods used, many of which are--or were--under
industrial property protection.
[0007] Such a method is disclosed in HU 204 481 ("Method for
mezophilic or thermophilic, aerobic enzyme-based conditioning of
liquid organic materials and biomasses"); HU 208 657 ("Apparatus
for anaerobic purification of sewage sludge") or HU 200 139
("Method for treating liquids and sludges containing organic
materials with environment damaging effects").
[0008] These methods and apparatuses for carrying out the methods
are not capable or have only a limited capability of processing
heterogeneous and dangerous materials.
[0009] A more complex solution is disclosed in HU 208659 ("Method
for complex processing and utilization of municipal and
agricultural wastes"). Although this method is theoretically
suitable for treating materials of various states of condition,
however, it is not suitable for treating wastes of foodstuff or
foodstuff-like wastes that require pasteurization. It has a further
drawback that, depending on the type of feed, it requires the
application of various additives, such as lime cream, phosphor,
potassium, etc. Yet another drawback is that the continuous
operation cannot be guaranteed and it has not been disclosed what
kind of apparatus can preferably be used to carry out the
method.
[0010] An object of the present invention is to provide a method
for economically and reliable processing various organic materials,
also including biologically degradable materials that requires
pasteurization, independently of their content and their state of
condition, in a single, preferably closed-loop, continuously
operating system.
[0011] Another object of the invention is to provide apparatuses:
crushing and sorting unit and heat treatment/mixing unit for the
system carrying out the method.
[0012] The invention is based on the idea that the very high amount
of sewage sludge produced in the sewage sludge purification plants
of the settlements day by day and the high amount of household
garbage and municipal waste produced in the same settlements, all
containing organic materials can be treated together in a complex
and economic manner.
[0013] We also recognised that the solid and/or liquid wastes
containing solid materials, as well as biologically non-degradable
mixed empties may be crushed and separated into a biologically
degradable organic fraction and a biologically non-degradable
fraction in one step, in a properly designed apparatus comprising
crushing screws, stirring screws, discharging screws and briar
teeth.
[0014] In addition, it was also recognised that in view of the
economy in space and the energy consumption, it is preferred that
the steps of heat treatment and mixing are carried out in one
integrated unit.
[0015] The method of processing and utilizing wastes with organic,
preferably high organic material content, comprises by the steps of
crushing the waste in a crushing unit; heat treating, if needed and
mixing the crushed material with the sewage sludge; homogenizing
the mixture; fermenting the homogenous material and directing the
biogas obtained into a gas tank, which method is characterized
according to the invention by that the waste is crushed to pieces
of 12 mm or smaller size, in a way that the empties are torn open
and the organic residues therein are discharged; the non degradable
waste is separated and the organic waste cleared from solid
components is processed.
[0016] The waste and sewage sludge to be homogenised is preferably
in the range of 1.2 to 0.8, more preferably 1.2 to 1.0 and
advantageously 1:1 by volume.
[0017] The solid material content of the sewage sludge homogenised
is preferably approximately 6%, at most 8%.
[0018] The temperature of the sewage sludge is held preferably in
the range of 35 to 55.degree. C. during homogenization.
[0019] The crushing and sorting unit according to the invention
comprises receiving tray, crushing screws and driving units,
wherein the bottom plate of the receiving tray is perforated and
formed as a screw house with an open upper part for receiving a
twin screw, two crushing screws are arranged in said screw house; a
chamber is formed under the bottom plate in order to accommodate
one or more stirring screws; and a discharging assembly having a
discharging screw is arranged at the end of the receiving tray
opposite to the crushing screw driving unit, in such a way that the
free end of the discharging screw opposite to the discharging screw
driving unit intrudes into the operational space of the receiving
tray), wherein the crushing screws are screws of the same pitch
direction and without central shaft, provided with short drive
shafts on their driven end, wherein the rotational axis of the
discharging screw and the plane determined by the rotational axes
of the two crushing screws define an acute angle.
[0020] On the end plate of the receiving tray there are preferably
a plurality of briar teeth and a plurality of bits are preferably
arranged on the end of the crushing screw.
[0021] The pitches of crushing screws may be made of multilayer
metal sheets, are preferably identical with each other and adapted
to rotate independently of each other meanwhile their rotational
speed may be adjustable. The non-driven end of the crushing screws
is arranged close to the end wall.
[0022] The discharging screw may turn back-and-forth and there may
be one or more separate discharge hoppers on the discharging
assembly.
[0023] The heat treatment/mixing unit according to the invention
comprises a heat treatment tank, a mixing tank and a mixer unit,
wherein the heat treatment tank is arranged at the upper part of
the mixing tank coaxially surrounding the mixing tank; and the heat
treatment tank and the mixing tank are interconnected by a quick
discharge assembly.
[0024] The heat treatment tank may be provided with internal and/or
external, and the mixing tank with external heat insulation. The
volume of the heat treatment tank is preferably less than the
volume of the mixing tank.
[0025] The invention will now be described in more detail with
reference to the accompanying drawings.
[0026] FIG. 1 illustrates the technological flow diagram and the
block diagram of the method and the system for implementing the
method according to the invention, respectively.
[0027] FIG. 2 shows a basic schematic line diagram of an exemplary
embodiment of the crushing and sorting unit according to the
invention, along a main sectional plane.
[0028] FIG. 3 is a schematic line diagram of the crushing and
sorting unit shown in FIG. 2, along a transversal sectional
plane.
[0029] FIG. 4 shows a schematic axonometric view of an exemplary
embodiment of the crushing and sorting unit according to the
invention, partly in section.
[0030] FIG. 5 is an enlarged detail (A) of FIG. 4
[0031] FIG. 6. shows a schematic axonometric view of the embodiment
of the crushing and sorting unit shown in FIG. 4. as viewed from
another viewing point.
[0032] FIG. 7. illustrates a basic schematic line diagram of an
exemplary embodiment of the heat treatment/mixing unit according to
the invention.
[0033] FIG. 8. shows an exemplary embodiment of the quick
discharging assembly of the heat treatment/mixing unit according to
the invention, illustrated in closed position.
[0034] FIG. 9. shows an exemplary embodiment of the quick
discharging assembly of the heat treatment/mixing unit according to
the invention, illustrated in open position.
[0035] For the sake of simplicity and better understanding of the
description, the following references are used: [0036] the solid
wastes and/or the mixture of solid and liquid wastes are referred
to as mixed waste A, independently of their content; [0037] the
liquid waste is referred to as liquid waste C, independently of its
content; [0038] the sewage sludge produced in place is referred to
as sewage sludge D; [0039] the delivered sewage sludge having a
solid material content equal to or less than 6% is referred to as
sewage sludge D'; [0040] the delivered sewage sludge having a solid
material content more than 6%, but less than 25% is referred to as
sewage sludge D''.
[0041] As shown in FIG. 1 the mixed waste A and/or the sewage
sludge D'' are fed into the crushing and sorting unit 1.
Alternatively, the liquid waste C and/or the sewage sludge D' may
also be fed into the system at this point.
[0042] The unit is used for crushing the waste into chips of
appropriate size--up to 8 mm--, and for separating the biologically
non-degradable materials from the organic fraction.
[0043] Hereafter the biologically degradable organic fraction will
be referred to as organic fraction B, whereas the biologically
non-degradable fraction will be referred to as wastes H and H'.
[0044] Waste H contains mainly inorganic materials.
[0045] Waste H' is a non-usable waste that contains a small amount
of organic material as well.
[0046] The organic fraction B of the mixed waste A is directed from
the crushing and sorting unit 1 into the mixing tank 32 or into the
heat treatment tank 31 of the heat treatment/mixing unit 3
corresponding to the position of the switching unit 2.
[0047] In case the waste, like the kitchen waste, requires
pasteurisation because of its content, the waste is first directed
into the heat treatment tank 31 and then into the mixing tank 32.
When pasteurisation is not necessary, these wastes are directly fed
into the mixing tank 32.
[0048] The biologically non-usable waste fractions H and H' of the
mixed waste A are directed from the crushing and sorting unit 1
into waste collection tanks 9d and 9d', respectively, for further
external processing.
[0049] The liquid waste C and/or the sewage sludge D' are directed
also through the drawing-off station 5 into the mixing tank 32 or
the heat treatment tank 31 of the heat treatment/mixing unit 3
corresponding to the position of the switching unit 2.
[0050] The appropriately pre-treated sewage sludge D and/or sewage
sludge D' are fed into the mixing tank 32 of the heat
treatment/mixing unit 3.
[0051] It is a matter of course that similarly to the organic
fraction B and the liquid waste C, the sewage sludge D and/or the
sewage sludge D' may also be fed through the switching unit 2 in
the same way as mentioned before.
[0052] The heat treatment/mixing unit 3 has a double function:
[0053] heat treatment and pasteurisation of wastes that require
pasteurisation, such as wastes of animal protein processing,
kitchen waste; [0054] mixing the organic fraction B and the liquid
waste C with the sewage sludge D and/or the sewage sludge D' so
that a sludge composition with a consistence suitable for
continuous fermentation be produced. This sludge composition will
be referred to as sludge composition E.
[0055] The mixing ratio of the waste A and/or the liquid waste C to
the total sewage sludge D and/or the sewage sludge D' is optimally
1 to 1 by volume, but it may vary in the range of 1.2 to 0.8,
preferably 1 to 1 by volume.
[0056] The solid material content of the sludge composition E is
optimally equal to or less than 6%, but it may vary between 2% and
8%.
[0057] The sludge composition E is fed into the fermentation unit
4. It is preferred that the fermentation unit 4 comprises both of a
thermophilic unit 41 and a mezophilic unit 42.
[0058] The fermentation unit 4 is used to ferment the sludge
composition E previously fed and to produce biogas from it.
[0059] The biogas G is directed from the fermentation unit 4 into
the gas tank 7 for further processing. The fermented sludge, also
referred to as fermented sludge F, is convayed into the sludge
treating block 9a for further processing.
[0060] FIGS. 2 to 5 show an exemplary embodiment of the crushing
and sorting unit according to the invention, which comprises a
hopper 101 for receiving the mixed waste A and/or the liquid waste
C and/or the sewage sludge D'' and for storing them during the
processing. The crushing and sorting unit 1 further comprises a
perforated filtering bottom plate 102 in the form of a screw house
with an open upper part, a chamber 103 arranged under said bottom
plate 102, a suction stub 104 connected the chamber 103 for
discharging the organic fraction B of the processed waste, a
receiving tray arranged on the end wall 105 and provided with briar
teeth 106, two crushing screws 11 arranged in the filtering bottom
plate 102, one or more sliding screws 12 arranged in the chamber
103, driving units 13 for the crushing screws 11, one or more
driving unit 14 for each of the sliding screws 12, a discharging
assembly 15 equipped with a discharging screw 151 for discharging
the biologically non-degradable fraction of the chipped waste, i.e.
the wastes H and H', said discharging assembly 15 being arranged at
the end of the receiving tray 10 opposite to the driving units of
the crushing screws and provided with a discharging screw driving
unit 152.
[0061] The discharging assembly 15 has one or more discharging
hoppers, in case of the above mentioned embodiment, two discharging
hoppers 153, 154, for discharging the wastes H and H'.
[0062] The crushing and sorting unit 1 is further provided with an
industrial water supplying pipe system 61 and a hot water supplying
pipe system 62.
[0063] The most important feature of the receiving tray 10 is the
perforated filtering bottom plate 102 formed as a screw house with
an open upper part, in which two crushing screws 11 are arranged in
parallel. The hopper 101 above the crushing screw 11 forms a high
capacity storage volume for receiving a large amount of waste at a
time.
[0064] The filtering bottom plate 102 of the receiving tray 10
formed as screw house with an open upper part is perforated and
adapted to properly guide the two crushing screws separately while
preventing them from being offset from their rotational axes. The
curvature of the filtering bottom plate 102 is very similar to the
curvature of the crest edge of the two crushing screws 11. The
filtering bottom plate 102 is removable and in case of wearing, it
may be replaced. The pattern of the perforation may be arbitrary,
whereas the recommended maximum size of the perforations D is 10 or
rather 8 mm, which allows solid materials still acceptable to pass
therethrough into the fermenter. Anyway, in several cases the size
of the perforations may be up to 12 mm. Beneath the filtering
bottom plate 102, there is a chamber 103 for receiving the liquid,
biologically degradable material, i.e. the mixed waste A and/or the
liquid waste C and/or the organic fraction B of the sewage sludge
D'', all of them being fed into the receiving tray 10. Inside the
chamber 103, one or more sliding screws 12 rotate to prevent any
deposition or blockage from being developed which would result in a
malfunction. The suction stub 14 of the pump used to convey the
organic fraction B for further processing is connected to the
chamber 103, the outlet of said suction stub being scraped, cleaned
and loosened by one of the sliding screws 12 of the chamber in
order to prevent any deposition from being developed on the suction
stub 104.
[0065] The two crushing screws 11 of the crushing and sorting unit
1 is used to carry out the substantial preparation and processing
operations. Its operation is supported by its construction. The
pitch and the rotational direction of the two crushing screws 11
are identical (both of the screws are either right-handed or
left-handed), thus their mutual seizure may be avoided even if the
crushing screws 11 rotate independently of each other. Due to the
independent rotation of the crushing screws, the material in the
receiving tray 10 may be forced to flow in various directions while
being stirred and chipped. Both of the crushing screws 11 are
formed without a central shaft, except a down-stream section of the
driving unit, where they are provided with a short stub shaft 112.
The section without shaft is required to have high elasticity and
flexibility, on the one hand, and high strength and high torque
transmission capability, on the other hand. Accordingly, it is made
of a multilayer plate resulting in high flexibility while having
high strength, heavy weight and high torque tolerating capability
at the same time. It has another very important feature: it has the
greatest possible diameter. The good preparation capability is due
to all of its diameter, its flexibility, its weight and its torque
tolerating capability.
[0066] The big solid, occasionally frozen pieces of material are
chopped and disgregated by the two crushing screws 11 at a high
efficiency. The filtering bottom plate 102 can clean and open up
the blocked perforations easily due to its capability of easily
fitting and easily evading obstacles as a result of its
flexibility, despite of its weight. It tears hardly any perforation
and due to its flexibility, it evades the forces in spite of that
there may be obstacles. A large diameter of at least 700 mm allows
solid materials (e.g. empties: cans, bottles, boxes and other
containers) to enter in or exit from between the screw threads. Due
to the absence of shaft, the flow is also allowed inside the closed
space of the screw leaf adjacent to the rotational axis, therefore
it performs a very definite and efficient crushing and recovering
operation of the bulk of the organic material.
[0067] The double crushing screw 11 has a further feature. At the
end adjacent to its driving unit and to its short screw section
with shaft, a cutting-tearing-crumbling mechanism with a plurality
of bits 111 is formed. According to the briar teeth 106 arranged on
the end plate 105 of the receiving tray 10, there is provided a
stationary row of bits, whereas on the end of the rotational
crushing screw 11, a moving row of bits is arranged, as it is
obvious from the above mentioned features. Thus the solid pieces in
the material flow moving towards the wall having the stationary
bits, including the beer cans as well, will be cut off and made
suitable for emptying.
[0068] The discharging assembly 15 equipped with a discharging
screw 151 and a discharging screw driving unit 152 for discharging
the biologically non-degradable fraction of the chipped waste, i.e.
the waste H, is arranged at the end of the receiving tray 10
opposite to the driving unit of the crushing screw 13. The axis of
the discharging screw 151 and the plane determined by the axes of
the crushing screws 11 define an acute angle. The discharging
assembly 15 starts to operate only when the charged waste has been
recovered, the major part of the organic fraction B has passed the
perforation and substantially, only the leached empties, solid
pieces and other wastes H have been retained.
[0069] The two crushing screws 11 are driven by means of a
frequency converter. It is preferred that an operator can control
the rotational direction and the shut-down of the crushing screws
11 independently by using a radio frequency, portable switching
device, thus it becomes possible for a properly skilled operator to
mix materials that contain pieces with size or condition which may
be dangerous for the machine. The non-driven end of the twin screw
is close to the end wall, thus the waste can be efficiently
discharged without leaving a dead zone.
[0070] In a preferred embodiment the hopper 101 of the receiving
tray 10 can be opened mechanically, and can be closed for safety
reasons, which allows to reduce the effects of smell and noise. A
suction cleaning system may also be connected thereto. For dilution
and flushing, hot flush water may be introduced into the inner
space of the receiving tray 10.
[0071] In order to allow an even better flush, shower-like water
injection should be provided. It is recommended to return some
sludge from the fermenter. Optionally, the pump conveying from the
apparatus to the fermenter is adapted for recirculation so that a
larger portion of the organic material can be washed.
[0072] In a preferred embodiment, the discharging assembly is a
high-performance machine as the discharging assembly 15 may be
filled up with material being fed into the receiving tray 10 for
separation. The discharging screw 151 of the discharging assembly
15 is than to be rotated in reverse direction in order to return
the mass with high organic content to the receiving tray 10 for
separation. In order to better compress the waste, the screws
should be able lifting the waste up to the half level, followed by
returning and repressing it.
[0073] On the discharging assembly 15, two discharging hopper 153,
154 are mounted for depositing the wastes H and H' in different
directions by type.
[0074] Under the discharging hoppers 153, 154, a compressing
machine may be arranged that compresses the foreign packaging
materials to be conveyed to the smallest possible volume. The
bottom plate of the concrete object lowered beneath the ground
level for receiving the apparatus is inclined and has an
accumulating dibhole for collecting the escaped liquids.
[0075] For the installation of the crushing and sorting unit 1, it
is recommended that the apparatus should be accessible by lorries
and heavy trucks and the road surface T in front of the apparatus
should be available for transportation manipulations. The apparatus
should protrude from the plane of the road surface T at a minimum
level in such a way that the plane of the hopper extends at a
distance of up to 500-1000 mm from the road surface. The protrusion
is provided to avoid an accident, however an excessive protrusion
would make it impossible for the tip lorries to reverse and to
discharge its load.
[0076] By using an adjustable protective screen, however, an
adequate prevention of accidents may be reached.
[0077] FIG. 7 illustrates a basic schematic line diagram of an
exemplary embodiment of the heat treatment/mixing unit according to
the invention, meanwhile FIGS. 8 and 9 show an exemplary embodiment
of the quick discharging assembly of the heat treatment/mixing unit
according to the invention, illustrated in the closed position and
in the open position, respectively. Further to the structure of the
heat treatment/mixing unit 3, these figures also illustrate
additional units and fittings that preferably enhance the operation
of said unit or that are necessary to use.
[0078] One of the basic requirements for the proper operation of
the anaerobic fermenters is to feed the material to be fermented
(i.e. the sludge) into the fermenter uniformly and, if possible,
continuously and in small doses rather than in bursts. The material
to be fed should be homogeneous, and its temperature should have a
value that does not disturb the biological system operating in the
fermenters. It is very difficult to satisfy these condition in the
case of lumpy organic materials originating from various locations,
wherein said materials are to be treated in an anaerobic
environment. If some portion of said materials should be
pasteurised (at 70.degree. C.) as well, the problem to be solved
would become even more complicated. Another significant difficulty
is that the anaerobic fermenters are extremely responsive to the
introduction of untreatable, lumpy materials. Such materials
accumulate on the bottom of the fermenters and after a certain
period, they block the pipes and the heat exchangers, which may
finally result in the shut-down of the fermenters.
[0079] The heat treatment/mixing unit 3 according to the invention
is formed of two stacked, double-wall metallic tank. On the upper
part of the cylindrical intermediate tank, i.e. the mixing tank 32,
a shorter second tank, i.e. the heat treatment tank 31, is fixed
outside, wherein the volume of the heat treatment tank 31 is less
than that of the inner mixing tank 32. The upper part is
constituted by the heat treatment tank 31 forming the
pasteurisation zone, whereas the intermediate part is constituted
by the mixing tank 32 forming the mixing zone. In the mixing tank
32, the pasteurised materials are recooled, and mixed and diluted
with the sewage sludge D produced by this technology. The mixing
tank 32 is also used to produce the homogeneous, uniform mixture
for feeding it into the fermentation units 4. Its internal volume
is greater than its external volume, which allows a quick discharge
of the pasteurisation zone into the mixing zone. The mixing zone is
equipped with a high-power mechanical mixer 33 that is adapted to
recool the pasteurised materials quickly.
[0080] The heat treatment tank 31 is preferably provided with a
first heat insulation 311 and an external heat insulation 312,
whereas the mixing tank 32 is provided with an external heat
insulation 312.
[0081] A powered quick discharging assembly 35, which can be opened
and closed by power, is used to discharge the two zones quickly
into each other by means of the gravitation. The discharging
assembly of large diameter prevents any deposition from developing
on the bottom of the pasteurisation zone. Due to its special
design, the two zone can co-operate in the open state, thus the
total capacity can be exploited. The mixing zone 38 is provided
with a heat exchanger for the mixing zone, and the pasteurisation
zone 37 is provided with a heat exchanger for the pasteurisation
zone. Due to the quick discharging assembly 35, the total capacity
may be used for pasteurisation if needed.
[0082] In this embodiment, the switching unit 2 is in the form of a
manifold 34 extending inside the mixing tank and penetrating at the
top of the mixing tank 32, where it branches off to form two pipe
sections, both of them being equipped with a powered slide gate,
wherein one of the branches is directed into the heat treatment
tank 31, whereas the other one is directed into the mixing tank 32.
The bottom of the manifold 34 is lead out downside, and the
materials fed therein for treatment are directed through the
macerator 341 into either the pasteurisation zone or the mixing
zone easily and in a very simple way due to the manifold 34. If
necessary, the material to be treated can be recirculated through
the macerator 341 during the pasteurisation as well in order to
make the treated material as fluent and uniform as possible with
the lowest possible heat loss, due to the application of the
manifold.
[0083] The volume of the internal tank 32 of the heat
treatment/mixing unit 3 is greater than that of the external heat
treatment tank 31, therefore a certain amount of cold sludge may be
stored in the internal tank. The mixing tank 32 is equipped with a
high-performance mechanical mixer 33 adapted to quickly recool the
pasteurised materials by mixing them rapidly with the cold sludge
stored therein.
[0084] The method according to the invention will be described with
reference to a sewage purification plant as an example.
[0085] In the sewage purification plant, the materials are utilized
or destroyed by means of anaerobic fermentation. The types and the
quantities of the used materials are listed below.
TABLE-US-00001 Rate of solid material Condition tons/day % Sewage
sludge (produced liquid 54 in place) Sewage sludge (delivered)
liquid 10 Wastes of animal protein liquid 25 processing Wastes of
dairy industry liquid/coarse 8 Kitchen waste coarse 2 Greasy sewage
liquid 1
[0086] The liquid wastes (wastes of animal protein processing,
greasy wastes, liquid wastes of dairy industry), as well as the
sewage sludge produced in other sewage purification plants (in
pre-concentrated state) may be delivered by tank vehicles of 6, 9
or 25 m.sup.3 capacity. The tank vehicles discharge the waste in a
closed system, the waste being directed by means of pumps into a
pasteurization zone of 65 m.sup.3 or a storage zone of 54 m.sup.3
(for sewage sludge) of the pasteurization unit.
[0087] The kitchen wastes are delivered in closed barrels of 50
litres or in closed containers with a volume of 9 m.sup.3 or 25
m.sup.3. Dairy products in cans or paperboards may be delivered on
pallets. At the waste receiving station 1 having a net capacity of
35 m3, both of barrels and tanks may be deposited. The two crushing
screws mounted in the drawing-off station presses the organic
fraction of the waste through a perforated bottom plate made of
carbon steel, said bottom plate having in this case a granular size
of 12 mm. The waste may be diluted by either sewage sludge or hot
water. The crushed waste is conveyed to the pasteurization unit by
means of stirring screws and pumps. The unrecoverable materials,
empties etc. may be removed by means of discharging screws that
perform water wash. The waste receiving station, the cover of which
can be closed, may be connected via an exhauster to a biofilter
used for aerobic biological degradation of the smelly
components.
[0088] At the receiving station, smell exhaustion must be provided.
The net capacity of the drawing-off station is 10 m.sup.3, while
the applied technology is the same as mentioned before.
[0089] The wastes directed through the crushing and grinding
machines (i.e. the coarse wastes) and the liquid wastes are
directed into the pasteurisation unit comprising the two separate
tanks. In the pasteurisation zone of said unit is used to carry out
the optional heat treatment (at 75.degree. C., the holding time is
1 hour). The wastes are heated by means of a heat exchanger. The
storage zone is used to mix the wastes with each other and with the
concentrated sewage sludge delivered to the plant or produced in
place, as well as to make the mixture uniform for feeding into the
anaerobic fermentation technology. The mixing ratio of the waste
and the sewage sludge is here approximately 1 to 1 by volume.
[0090] Subsequently, the mixed wastes are first fed into the
thermophilic anaerobic fermenters (operating temperature:
55.degree. C., net capacity: 2000 m.sup.3), where the fermentation
is completed at a high efficiency during a 10 day holding time. The
substantially fermented sludge discharged from the thermophilic
unit and the major part of the concentrated sewage sludge produce
in place are fed into the mezophilic anaerobic fermenters
(operating temperature: 35.degree. C., net capacity: 3.times.3000
m.sup.3), where they become fermented during a 14-16 day holding
time. The assumed degradation efficiency of the
thermophilic-mezophilic system is 55-60% in respect of the organic
material content, and the expected specific biogas production (for
1 ton of degraded organic material) is in the range of 1100 to 1400
Nm.sup.3.
[0091] The gasification of the fermented sludge and the storage
thereof before dehydration are carried out in a post-fermenter (net
capacity: 3000 m.sup.3) operating at variable operating levels
without heating and mixing.
* * * * *